Two-wheeled recovery trailers

ABSTRACT

A trailer ( 10 ) for the recovery of vehicles has a drawbar ( 12 ) having first and second sections ( 14,16 ) hinged together at adjacent ends, about a horizontal transverse axis; the first section ( 14 ) of the drawbar ( 12 ) has a ball cup ( 24 ) by which it may be secured to a towing hitch ( 100 ) of a recovery vehicle, the second section ( 16 ) of the drawbar ( 12 ) has a pair of arms ( 30 ) pivotally mounted adjacent the end thereof remote from the end hinged to the first section ( 14 ), the arms ( 30 ) are pivotal between a stowed position in which they are disposed parallel to the drawbar ( 12 ) and a deployed position in which they are disposed coaxially of one another on an axis transverse to the longitudinal axis of the drawbar ( 12 ); a pair of wheel pans ( 50 ) are mounted and able to slide, one on each of the arms ( 30 ), the wheel pans ( 50 ) are interconnected to the second section ( 16 ) of the drawbar ( 12 ) by a linkage mechanism ( 60, 62 ), so that when the arms ( 30 ) are in the stowed position, the wheel pans ( 50 ) are slid inwardly towards the pivot connections of the arms ( 30 ) to the drawbar ( 12 ) and, when the arms ( 30 ) are in the deployed position, the wheel pans ( 50 ) being slid outwardly towards the free ends of the arms ( 30 ); a self steering wheel ( 70 ) being mounted on each of the arms ( 30 ), the self steering wheels ( 70 ) being disposed outboard of the wheel pans ( 50 ) when the arms ( 30 ) are in the deployed position.

The present invention relates to trailers and in particular to trailersused by recovery vehicles, the trailers being adapted to support thewheels on one axle of the vehicle being recovered.

One form of trailer for use in the recovery of vehicles comprises adrawbar which may be attached to the towing hitch of the recoveryvehicle. A cross-member is mounted transversely on the drawbar, thecross-member having wheels mounted at each end. Inboard of the wheelsare a pair of wheel pans, which are adapted to support either the frontor rear wheels of the vehicle being recovered. The wheel pans may bemounted on the cross-member so that they are adjustable laterally inorder to accommodate vehicles with different tracks. The wheel base ofthe trailer is however normally fixed.

When not in use, because of the size of the trailer, it would normallybe stowed externally of the recovery vehicle, unless the trailer may bepartially dismantled to be stowed within the recovery vehicle.

The present invention provides a compact recovery trailer which may bestowed completely within a normal recovery vehicle, for example a panelvan, and may be rapidly deployed and rapidly stored after use.

In accordance with one aspect of the present invention, a trailer forthe recovery of vehicles comprises:

-   -   a drawbar with means for attachment to a towing vehicle, a pair        of wheels attached to the drawbar and a pair of wheel pans        secured to the draw bar, characterised in that:    -   the drawbar has first and second sections, the first and second        sections being hinged together at adjacent ends, about a        horizontal transverse axis;    -   the first section of the drawbar having means by which it may be        secured to a towing hitch of a recovery vehicle, at an end        thereof remote from the end hinged to the second section;    -   the second section of the drawbar having a pair of arms        pivotally mounted adjacent an end thereof remote from the end        hinged to the first section, the arms being pivotal between a        stowed position in which they are disposed parallel to the        drawbar, one on either side of the drawbar in juxtaposed        relationship thereto, to a deployed position in which they are        disposed coaxially of one another, on an axis transverse to the        longitudinal axis of the drawbar;    -   the wheel pans being mounted and able to slide, one on each of        the arms, the wheel pans being interconnected to the second        section of the drawbar by a linkage mechanism, so that when the        arms are in the stowed position, the wheel pans are slid        inwardly towards the pivot connections of the arms to the        drawbar and, when the arms are in the deployed position, the        wheel pans being slid outwardly towards the free ends of the        arms; and    -   a self steering wheel being mounted on each of the arms, the        self steering wheels being disposed outboard of the wheel pans        when the arms are in the deployed position.

With the trailer described above, when the arms are in the deployedposition the trailer may be attached to the towing hitch of a recoveryvehicle to allow a vehicle to be towed as with conventional trailers ofthis type. However, when not in use, the arms of the trailer with thewheel pans and self steering wheels attached thereto may be moved to thestowed position and the drawbar may be folded about its hinge point, toform a compact assembly, which may easily be stowed in the back of anormal recovery vehicle.

According to a preferred embodiment of the invention, a pivot bracket ispreferably provided in the back of the recovery vehicle to which thefree end of the first section of the drawbar may be pivotally attached.A winch may also be provided by which pivoting of one section of thedrawbar relative to the other may be controlled. The winch may also beused to recover the broken down vehicle and pull in onto the trailer.

Means, for example a screw mechanism or hydraulic and pneumatic means,may also be provided for moving the arms between their deployed andstowed positions.

According to a preferred embodiment of the invention, the linkagemechanism connecting the wheel pans to the drawbar may be adjustable toadjust the position of the wheel pans to match the track of the vehiclebeing recovered. Furthermore, the self steering wheels are preferablysecured to the wheel pans so that the track of the trailer will also beadjusted with the wheel pans.

It is also desirable that the self steering wheels are interconnected sothat the steering angles of the two wheels are the same and to preventthe wheels from vibrating independently due to single wheel impacts, forexample when one of the wheels is subjected to a discreet disturbancesuch as a pothole or kerb strike. The two wheels may be interconnectedby a mechanical link, such a link would however have to be articulatedto accommodate movement of the arms and adjustable to accommodatevariation in the track. According to a preferred embodiment, the wheelsare interconnected hydrostatically, each wheel having a steering armwhich is connected to a double acting ram, the two rams beinginterconnected by means of flexible hose so that as one of the wheelspivots about its axis the movement is transmitted to the other wheel.

The present invention is now described, by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 is a plan view of a trailer in accordance with the presentinvention, in its deployed configuration;

FIG. 2 shows a front view of the trailer illustrated in FIG. 1, in itsstored configuration;

FIG. 3 shows a perspective view of the trailer in its storedconfiguration;

FIG. 4 shows a side elevation of the trailer shown in FIG. 1,illustrating a first stage of deployment of the trailer;

FIG. 5 shows a plan view of the trailer shown in FIG. 1, illustrating asecond stage of the deployment of the trailer;

FIG. 6 shows a detailed perspective view of a wheel pan and wheel of thetrailer illustrated in FIG. 1; and

FIG. 7 illustrates diagrammatically a hydrostatic steering linkage forthe trailer illustrated in FIG. 1.

As illustrated in the drawings, a trailer 10 has a drawbar 12. Thedrawbar 12 is formed in two sections, a forward section 14 and arearward section 16. The forward and rearward sections 14,16 are pivotedtogether about adjacent ends, by pivot pin 18 so that the sections 14and 16 may be disposed end to end, or the rearward section 16 may befolded underneath the forward section 14. The end of the forward section14 extends beyond the pivot pin 18 and has apertures therein, theapertures aligning with corresponding apertures in the rearward section16 when sections 14 and 16 are disposed end to end, so that a lockingpin 20 may be inserted through the apertures, to lock the drawbar in itsextended position. A stop (not shown) is provided to prevent thesections 14 and 16 going past the position in which the apertures arealigned.

A pair of gas struts 22 are provided between the forward and rearwardsections 14 and 16 of the drawbar 12 to assist and control relativemovement of the sections 14 and 16, as the drawbar 12 is moved betweenits folded and extended positions.

A towing hitch, for example a ball joint cup 24 is secured to theforward end of position 14 of the drawbar 12, for attachment to a towinghitch 100 of the recovery vehicle. A pair of trunions 26 are alsoprovided adjacent the forward end of the forward section 14 of drawbar12, one extending to each side thereof.

A pair of arms 30 are pivotally mounted to a bracket 31 secured to therear end of the rearward section 14 or the drawbar 12. The arms 30 aremounted by means of pivot pins 32, for movement in the plane of the rearsection 16 of the drawbar 12. The arms 30 extend beyond the pivot pins32 and a pair of links 34 extend from the end of each arm 30 to a block36 mounted for axial movement on a lead screw 38. A drive formation 40is provided on the lead screw 38 by which the lead screw 38 may berotated to move the block 36 linearly, causing the arms 30 to pivotabout pins 32, between a stowed position in which the arms 30 aredisposed parallel and in juxtaposed relationship to the rearward section14 of the drawbar 12, as illustrated in FIGS. 2 and 3; and a deployedposition in which the arms 30 extend transversely of the axis of thedrawbar 12, as illustrated in FIG. 1. In the deployed position,apertures at the end of arm 30 are aligned with apertures 42 in thebracket 31 so that locking pins 44 may be located through apertures 42,to lock the arms 30 in their deployed positions.

A pair of wheel pans 50 has tubular mounting means 52, which locate andslide one on each of the arms 30. The wheel pans 50 define a platformfor the wheels of the towed vehicle. Spring loaded adjustable chocks 54are provided at the rearward end of the pans 50, which will be depressedas the wheel of the vehicle is moved onto the pan 50 and will spring upto help retain the towed vehicle on the trailer 10. Additional fasteningmeans, for example straps or chains are also provided for securing thetowed vehicle.

Links 60 are pivotally connected between the pans 50 and projections 62on the bracket 31, the links 60 causing the wheel pans 50 to slideoutwardly on arms 30 as the arms are moved between their stored anddeployed positions and to slide inwardly on arms 30 as the arms 30 aremoved between their deployed and stowed positions. The links 60 aresecured to the projections 62 by means of locking pins 64 which engagethrough aperture 66 in the ends of links 60 and projections 62. Severalapertures 66 are provided in both the links 60 and projections 62, bywhich the effective length of the links 60 may be adjusted. Theseparation of the wheel pans 50 when the arms 30 are in their deployedpositions, may thereby be adjusted to suit the track of the towedvehicle.

A pair of self steering wheels 70 are mounted one on each of the wheelpans 50, the self steering wheels 70 being mounted on the outside of thewheel pans 50, when the arms 30 are in their deployed positions. Theself steering wheels 70 are mounted on kingpins 72 which extendsubstantially vertically but are inclined at appropriate camber andcastor angles to provide a self-steering effect. Steering levers 74 areprovided on each of the self steering wheels 70, the steering levers 74being connected to double-acting rams 76 mounted on the wheel pans 50.The rams 76 on either side of the trailer 10 are interconnected byflexible hydraulic hoses 78, the forward chamber of one ram 76 beingconnected to the forward chamber of the other ram 76 and the rearwardchamber of one ram 76 being connected to the rearward chamber of theother ram 76. The connected chambers thereby form closed hydrauliccircuits by which any steering movement of one wheel 70 will betransmitted to the opposite wheel 70. For example, when the left wheel70 is steered to the left due to its self steering properties, thevolume of the forward chamber 84 on the left ram 76 decreases forcingfluid to be transferred to the forward chamber 84 on the right ram 76causing the right wheel 70 to be steered to the left. This steeringmotion causes the volume of the rearward chamber 86 of the right ram 76to decrease and forces fluid into the rearward chamber 86 of the leftram 76, which is consistent with the applied steering motion. This fluidtransfer works in the opposite sense to steer both wheels 70 to theright.

In this manner, the wheels 70 will remain in phase to minimise tyrescrub and steering shimmy, particularly when the trailer 10 is subjectedto any uneven forces, for example, when one wheel 70 is subject todiscreet disturbance such as a pothole or kerb strike. Furthermore,interlinking of the wheels 70 in this manner will resist and damp outany unwanted motion of the wheels 70. The amount of steering damping canbe varied by adjusting the sizes of the hoses 78 or fitting restrictors82, to control the rate of flow of fluid.

An isolation valve 80 may be provided between the rams 76, in order tolock the wheels 70 when, for example, reversing.

The use of flexible hoses 78 as described above allows for movement ofthe wheels 70 between the deployed and stowed positions of the trailer10 and also permits adjustment of the track of the trailer 10.

In the stowed position, as illustrated in FIG. 2, the trailer isdisposed substantially vertically in the rear of the recovery vehicle,the trunions 26 on the forward section 14 of the drawbar 12 engaging apivot bracket 90 which is mounted to the floor of the recovery vehicle.The stowed trailer 10 may be locked in position in the recovery vehicleby, for example, means of the locking pin 20 which may engage aperturesin a suitable locking bracket 92 mounted within the recovery vehicle.

A winch 94 may also be provided in the recovery vehicle, the winch cable96 passing over pulley means 98 and being secured to the drawbar 12adjacent the interconnection of the forward and rearward sections 14, 16thereof.

To deploy the trailer the locking pin 20 is released from the bracket 92within the recovery vehicle and the forward section 14 of the drawbar 12is permitted to pivot rearwardly about trunions 26, movement thereofbeing controlled by the winch 94. As the forward section 14 pivotsrearwardly the rearward section 16 of the drawbar 12 pivots away fromthe forward section 14 under the influence and control of the gas struts22.

When the wheel pans 50 and wheels 70 are clear of the recovery vehicle,as illustrated in FIG. 3, the locking pins 64 may be engaged throughsuitable apertures 66 in the links 60 and projections 62 on bracket 31,to provide an appropriate separation of the wheel pans 50 to match thetrack of the vehicle to be towed.

The lead screw 38 may then be rotated to pivot arms 30 outwardly, asillustrated in FIG. 5, until the arms 30 extend transversely of thelongitudinal axis of the drawbar 12. Locking pins 44 are then locatedthrough the apertures in the ends of arms 30 and apertures 42 in thebracket 31 to lock the arms 30 in position.

The forward section 14 of drawbar 12 is then lowered further by means ofthe winch 94 until the forward and rearward sections are brought to thefully deployed position, when the locking pin 20 is located through thealigned apertures therein. As the forward section 14 of the drawbar 12is lowered, small rollers 58 at the rear of the wheel pans 50 will firstengage the ground permitting the wheel pans 50 to move backwardly untilthe self steering wheels 70 come into engagement with the ground.

After the sections 14,16 of the drawbar 12 have been locked in thedeployed position by pin 20, the front of the drawbar 12 may then belifted, either manually or by means of the winch 94, from the mountingbracket 90 and the ball joint cup 24 engaged with the towing hitch 100of the recovery vehicle.

Detachable ramps (not shown) are then attached to the trailing edge ofthe wheel pans 50 and the winch 94 is used to draw the vehicle beingrecovered onto the wheel pans 50 and the vehicle is located and securedto the trailer 10 using the adjustable wheel chocks 54 and restrainingstraps.

The reverse procedure is used to stow the trailer 10 after use.

Various modifications may be made without departing from the invention.For example while in the above embodiment a winch 94 is used todeploy/stow the trailer 10 and to draw the vehicle being recovered ontothe trailer 10, a dedicated power drive, for example an electric orhydraulic drive may be provided to deploy/stow the trailer 10. Alsowhile a leadscrew 38 is used to deploy the arms 30, other means, forexample a hydraulic or pneumatic ram, may be used for this purpose.

The locking pins 20, 44 used to lock the drawbar 20 and arms 30 in theirdeployed positions may be replaced by any suitable, releasable latchmeans.

In a further embodiment of the invention the wheels of the trailer 10may be secured directly to the arms 30, so that the track of the trailer10 is fixed or is adjustable independently of the wheel pans 50.

1. A trailer (10) for the recovery of vehicles comprising: a drawbar(12) with means (24) for attachment to a towing vehicle, a pair ofwheels (70) attached to the drawbar (12) and a pair of wheel pans (50)secured to the drawbar (12) characterized in that: the drawbar (12) hasfirst and second sections (14, 16), the first and second sections (14,16) being hinged together at adjacent ends, about a horizontaltransverse axis; the first section (14) of the drawbar (12) having means(24) by which it may be secured to a towing hitch (100) of a recoveryvehicle, at an end thereof remote from the end hinged to the secondsection (16); the second section (16) of the drawbar (12) having a pairof arms (30) pivotally mounted adjacent an end thereof remote from theend hinged to the first section (14), the arms (30) being pivotalbetween a stowed position in which they are disposed parallel to thedrawbar (12), one on either side of the drawbar (12) in juxtaposedrelationship thereto and a deployed position in which they are disposedcoaxially of one another on an axis transverse to the longitudinal axisof the drawbar (12); the wheel pans (5) being mounted and able to slide,one on each of the arms (30), the wheel pans (50) being interconnectedto the second section (16) of the drawbar (12) by a linkage mechanism(60, 62), so that when the arms (30) are in the stowed position, thewheel pans (50) are slid inwardly towards the pivot connections of thearms (30) to the drawbar (12) and, when the arms (30) are in thedeployed position, the wheel pans (50) being slid outwardly towards thefree ends of the arms (30); and a self steering wheel (70) being mountedon each of the arms (30), the self steering wheels (70) being disposedoutboard of the wheel pans (50) when the arms (30) are in the deployedposition.
 2. The trailer (10) according to claim 1, wherein thereleasable locking means (20) is provided between the first and secondsections (14, 16) of the drawbar (12), to lock the drawbar (12) in thedeployed position.
 3. The trailer (10) according to claim 2, wherein alocking pin (20) engages through aligned apertures in the first andsecond sections (14, 16) of the drawbar (12) the lock the drawbar (12)in the deployed position.
 4. The trailer (10) according to claim 1,wherein releasable means (44) is provided to lock the arms (30) in theirdeployed position relative to the second section (16) of the drawbar(12).
 5. The trailer (10) according to claim 4, wherein locking pins(44) engage through aligned apertures in the arms (30) and the secondsection (16) of the drawbar (12).
 6. The trailer (10) according to claim1, wherein the means (22) are provided to assist and control relativemovement is the first and second sections (14, 16) of the drawbar (12)as they are moved between their stowed and deployed positions.
 7. Thetrailer (10) according to claim 6, wherein one or more gas struts (22)act between the first and second sections (14, 16) of the drawbar (12).8. The trailer (10) according to claim 1, wherein the linkage mechanisms(60, 62) between the wheel pans (50) and the second section (16) of thedrawbar (12) are adjustable, to permit adjustment of the lateralposition of the wheel pans (50).
 9. The trailer (10) according to claim8, wherein a link (60) pivotally attached to each wheel pan (50) ispivotally attached to a formation (62) on the second section (16) of thedrawbar (12) by means of a pin (64) which engages through alignedapertures (66) in the link (6) and the formation (62), a plurality ofapertures (66) being provided in the link (60) and/or the formation (62)to permit adjustment of the linkage mechanism (60, 62).
 10. The trailer(10) according to claim 1, wherein the means (34, 36, 38) is providedfor moving the arms (30) between the stowed and deployed positions. 11.The trailer (10) according to claim 10, wherein the drive meanscomprises a pair of links (34), each link (34) being mounted at one endto one of the arms (3), the other end of each link (34) being mounted tolinear drive means (38), so that movement of the drive means (38) in onedirection will move the arms from their stowed to their deployedpositions and movement of the drive means in the opposite direction willmove the arms (3) from their deployed to their stowed positions.
 12. Thetrailer (10) according to claim 11, wherein the linear drive means (38)is a leadscrew, hydraulic or pneumatic ram.
 13. The trailer (10)according to claim 1, wherein the self steering wheels (70) are mountedon the wheel pans (50).
 14. The trailer (10) according to claim 1,wherein the self steering wheels (70) are interconnected so that theywill adopt the same steering angle.
 15. The trailer (10) according toclaim 14, wherein the self steering wheels (70) are interconnectedhydrostatically.
 16. The trailer (10) according to claim 15, wherein theself steering wheel s (70) each have a steering arm (74) which isattached to a double acting ram (76); a first chamber (84) on the ram(76) attached to one wheel (70) being connected to a first chamber (84)on the ram (76) attached to the other wheel (70); and a second chamber(86) on the ram (76) attached said one wheel (70) being connected to asecond chamber (86) on the ram (76) attached to said other wheel (70),by hydraulic hoses (78), to form closed hydraulic circuits; so themovement of one wheel (70) will be transmitted to the other wheel (70).17. The trailer (10) according to claim 16, wherein restrictors (82) areprovided in the hoses (78) to provide damping.
 18. The trailer (10)according to claim 16, wherein an isolation valve (80) is provided in atleast one hydraulic hose (78) by which the position of the self steeringwheels (70) may be locked.
 19. The trailer (10) according to claim 1,wherein means (26) is provided for pivotally mounting the trailer (10)in a recovery vehicle.
 20. The trailer (10) according to claim 19,wherein trunions (26) are provided for engagement of a bracket (90)mounted within a recovery vehicle.
 21. The trailer (10) according toclaim 1, wherein means (94) is provided for controlling movement of thetrailer (10) between its stowed and deployed positions.
 22. The trailer(10) according to claim 21, wherein said means (94) comprises a winch.23. The trailer (10) according to claim 1, wherein means (92) isprovided for locking the trailer (10) in a stowed position, within arecovery vehicle.